This is a good article about editing, using examples from Citizen Kane, Raiders of the Lost Ark, and more:
The ending of "North by Northwest" contains a famous edit that collapses a lot of time and what could have been a lot of unnecessary exposition and creates a very quick, short and satisfying happy ending (SPOILERS). In the climax of the movie, Cary Grant struggles to hold onto Eva Marie Saint's hand as she dangles over the side of a cliff. Then the film cuts to a shot of Grant lifting Saint up into a train berth as they enjoy a ride off into the sunset. So the film completely skips over the resolution of whether he will be able to hold onto her as she struggles to hang on, and the wrap-up of the mystery/spy story, both of which are unnecessary at that point. We all know she won't fall to her death, because that would be unsatisfying and dramatically it would have no point, and we already know the villains have been caught or killed and we know what they were doing and why. Any more recap would be redundant and boring.